import java.util.Scanner;

public class code5 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] cost = new int[n];
        for (int i = 0; i < n; i++) {
            cost[i] = sc.nextInt();
        }
        //动态规划
        int[] dp = new int[n+1];//由于得到最上面一个位置+1，所以得多开一个位置
        dp[0] = dp[1] = 0;
        for (int i = 2; i <= n; i++) {
            dp[i] = Math.min(dp[i-1]+cost[i-1],dp[i-2]+cost[i-2]);
        }
        System.out.println(dp[n]);
    }
}
